Methods of configuring additive-manufacturing machines

ABSTRACT

A method of configuring an additive-manufacturing machine comprises a chamber , a platform, movable inside the chamber and comprising a build-plane surface, and a laser, having a laser focal plane within the chamber. The method comprising steps of flowing a gas within the chamber in accordance with a first set of process parameters and identifying a value of a flow characteristic of the gas at a predetermined point in the laser focal plane while flowing the gas within the chamber in accordance with the first set of process parameters. The method also comprises additively manufacturing a test coupon using the laser while flowing the gas within the chamber in accordance with the first set of process parameters , wherein the test coupon has a test-coupon peripheral surface.

BACKGROUND

Additive manufacturing uses a layer-upon-layer approach to buildthree-dimensional parts. This approach enables parts with complex shapesto be produced, such as hollow parts or parts with internal trussstructures. Selective laser sintering (SLS) is an additive-manufacturingprocess that utilizes a laser beam to sinter powdered materials (e.g.,plastic, metal, ceramic) and to convert these materials into solidstructures. Specifically, a laser beam is directed at a powder layer,positioned at the laser focal plane. The laser beam selectivelytransforms portions of this powder layer into solidified material. Theremaining portions of the powder layer are eventually removed. SLS canintroduce fumes and other contaminants into the processing environment.These contaminants need to be removed, at least from the laser line ofsight, to minimize the interference with the laser beam. Gasrecirculation systems have been proposed for such contamination removalwithin additive-manufacturing machines. However, gas flow variations caninterfere with the decontamination efficiency and cause randomimperfections, inclusions, and voids in the sintered parts. Furthermore,these gas flow variations can be caused by various internal factors thatare not being directly controlled, such as filter clogging and the like.

SUMMARY

Accordingly, apparatuses and methods, intended to address at least theabove-identified concerns, would find utility.

The following is a non-exhaustive list of examples of the subjectmatter, disclosed herein.

Disclosed herein is a method of configuring an additive-manufacturingmachine that comprises a chamber, a platform, movable inside the chamberand comprising a build-plane surface, and a laser, having a laser focalplane within the chamber. The method comprises steps of flowing a gaswithin the chamber in accordance with a first set of process parametersand identifying a value of a flow characteristic of the gas at apredetermined point in the laser focal plane while flowing the gaswithin the chamber in accordance with the first set of processparameters. The method also comprises additively manufacturing a testcoupon using the laser while flowing the gas within the chamber inaccordance with the first set of process parameters, wherein the testcoupon has a peripheral surface. The method further comprises comparinga value of a physical property at a predetermined location on orunderneath the peripheral surface of the test coupon to a desired valueof the physical property. The method additionally comprises flowing thegas within the chamber in accordance with a second set of processparameters, different from the first set of process parameters, when adifference between the value of the physical property at thepredetermined location on or underneath the peripheral surface of thetest coupon and the desired value of the physical property is outside ofa predetermined range.

The value of the physical property at the predetermined location on orunderneath the peripheral surface of the test coupon indicates whetherthe additive-manufacturing machine can be used for manufacturing actualparts, e.g., when the difference is within the predetermined range. Thevalue is indicative of the expected properties of the manufacturedparts. At the same time, this depends on the process parameters used foradditive manufacturing of the test coupon. Specifically, this valuedepends on the first set of the process parameters used to flow the gaswithin the chamber. As such, any changes to these process parameters canresult in changes to the value of the physical property at thepredetermined location on or underneath the peripheral surface of thetest coupon. This feedback is used to determine process parameters thatyield the desired value of the physical property, e.g., the one withinthe predetermined range. Process parameters can be changed (e.g., fromthe first set of process parameters to the second set of processparameters) until the difference between the value of the physicalproperty at the predetermined location on or the underneath peripheralsurface of the test coupon and the desired value of the physicalproperty is within the predetermined range.

Also disclosed herein is a method of configuring anadditive-manufacturing machine that comprises a chamber, a platform,movable inside the chamber and comprising a build-plane surface, and alaser, having a laser focal plane within the chamber. The methodcomprises steps of flowing a gas within the chamber in accordance with afirst set of process parameters and identifying a value of a flowcharacteristic of the gas at a predetermined point in the laser focalplane while flowing the gas within the chamber in accordance with thefirst set of process parameters. The method also comprises simulatingthe step of flowing the gas within the chamber based on the value of theflow characteristic of the gas at the predetermined point in the laserfocal plane so that a value of a simulated-flow characteristic of thegas at a predetermined point away from the laser focal plane isidentified. The method further comprises comparing the value of thesimulated-flow characteristic of the gas at the predetermined point awayfrom the laser focal plane to a desired value of the simulated-flowcharacteristic. The method additionally comprises flowing the gas withinthe chamber in accordance with a second set of process parameters,different from the first set of process parameters, when a differencebetween the value of the simulated-flow characteristic of the gas at thepredetermined point away from the laser focal plane and the desiredvalue of the simulated-flow characteristic is outside of a predeterminedrange.

Simulating the step of flowing the gas within the chamber based on thevalue of flow characteristic of the gas at the predetermined point inthe laser focal plane can be used instead of additively manufacturingtest coupon (e.g., to expedite the system qualification) or in additionto additively manufacturing the test coupon (e.g., to provide additionalfeedback). The value of flow characteristic of the gas is used as aninput to this simulation. For example, the flow characteristic of thegas can be a linear speed of the gas as the gas flows through thechamber. This value depends on the first set of process parameters usedto flow the gas within the chamber. As such, any changes to theseprocess parameters can result in changes to the value of simulated-flowcharacteristic of the gas at the predetermined point away from the laserfocal plane. This feedback is used to determine the process parametersthat yield the desired value of the simulated-flow characteristic, e.g.,the one within the predetermined range. Process parameters can bechanged (e.g., from the first set of process parameters to the secondset of process parameters) until the difference between the value of thesimulated-flow characteristic and the desired value of the physicalproperty is within the predetermined range.

Further disclosed herein is a method of monitoring the operation of anadditive-manufacturing machine that comprises a chamber, a platform,movable inside the chamber and comprising a build-plane surface, and alaser, having a laser focal plane within the chamber. The methodcomprises flowing a gas within the chamber in accordance with a firstset of process parameters and identifying a value of a flowcharacteristic of the gas at a predetermined point in the laser focalplane while flowing the gas within the chamber in accordance with thefirst set of process parameters. The method further comprises comparingthe value of the flow characteristic of the gas at the predeterminedpoint in the laser focal plane to a desired value of the flowcharacteristic to determine a difference therebetween. The method alsocomprises additively manufacturing a part using the laser while flowingthe gas within the chamber in accordance with the first set of processparameters only when the difference between the value of the flowcharacteristic of the gas at the predetermined point in the laser focalplane and the desired value of the flow characteristic is within apredetermined range.

The desired value of flow characteristics can be used as a directreference to determine if the additive-manufacturing machine is readyfor manufacturing the part. This direct reference eliminates the needfor additively manufacturing test coupons and testing these couponsthereafter. Furthermore, this direct reference eliminates the need forsimulations and computational-fluid-dynamics analysis. For example, thedesired value of flow characteristic can be established previouslyduring validation and/or qualification of the additive-manufacturingmachine.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made to the accompanying drawings, which are notnecessarily drawn to scale, and where like reference charactersdesignate the same or similar parts throughout the several views. In thedrawings:

FIG. 1 is a block diagram of an additive-manufacturing machine,according to one or more examples of the subject matter, disclosedherein;

FIG. 2A is a schematic side cross-sectional view of theadditive-manufacturing machine of FIG. 1 while additively manufacturinga test coupon or part, according to one or more examples of the subjectmatter, disclosed herein;

FIG. 2B is a schematic side cross-sectional view of theadditive-manufacturing machine of FIG. 1 while identifying the flowcharacteristic of the gas, flowing through the chamber of theadditive-manufacturing machine, according to one or more examples of thesubject matter, disclosed herein;

FIGS. 2C and 2D are schematic side cross-sectional views of aflow-characterization system for identifying the flow characteristic ofthe gas flowing through the chamber of the additive-manufacturingmachine of FIG. 1 , illustrating different positions of an extensiblepressure probe, according to one or more examples of the subject matter,disclosed herein;

FIG. 2E is a schematic side cross-sectional view of theflow-characterization system of FIGS. 2C and 2D, illustratingreference-plate openings, according to one or more examples of thesubject matter, disclosed herein;

FIGS. 3A, 3B, 4, and 5 are process flowcharts, corresponding to methodsof configuring the additive-manufacturing machine of FIG. 1 , accordingto one or more examples of the subject matter, disclosed herein;

DETAILED DESCRIPTION

In FIG. 1 , referred to above, solid lines, if any, connecting variouselements and/or components may represent mechanical, electrical, fluid,optical, electromagnetic, and other couplings and/or combinationsthereof. As used herein, “coupled” means associated directly as well asindirectly. For example, a member A may be directly associated with amember B, or may be indirectly associated therewith, e.g., via anothermember C. It will be understood that not all relationships among thevarious disclosed elements are necessarily represented. Accordingly,couplings other than those depicted in the block diagrams may alsoexist. Dashed lines, if any, connecting blocks designating the variouselements and/or components represent couplings similar in function andpurpose to those represented by solid lines; however, couplingsrepresented by the dashed lines may either be selectively provided ormay relate to alternative examples of the subject matter, disclosedherein. Likewise, elements and/or components, if any, represented withdashed lines, indicate alternative examples of the subject matter,disclosed herein. One or more elements shown in solid and/or dashedlines may be omitted from a particular example without departing fromthe scope of the subject matter, disclosed herein. Environmentalelements, if any, are represented with dotted lines. Virtual (imaginary)elements may also be shown for clarity. Those skilled in the art willappreciate that some of the features illustrated in FIG. 1 may becombined in various ways without the need to include other featuresdescribed in FIG. 1 , other drawing figures, and/or the accompanyingdisclosure, even though such combination or combinations are notexplicitly illustrated herein. Similarly, additional features notlimited to the examples presented may be combined with some or all ofthe features shown and described herein.

In the following description, numerous specific details are set forth toprovide a thorough understanding of the disclosed concepts, which may bepracticed without some or all of these particulars. In other instances,details of known devices and/or processes have been omitted to avoidunnecessarily obscuring the disclosure. While some concepts will bedescribed in conjunction with specific examples, it will be understoodthat these examples are not intended to be limiting.

Unless otherwise indicated, the terms “first,” “second,” etc. are usedherein merely as labels and are not intended to impose ordinal,positional, or hierarchical requirements on the items to which theseterms refer. Moreover, reference to, e.g., a “second” item does notrequire or preclude the existence of, e.g., a “first” or lower-numbereditem, and/or, e.g., a “third” or higher-numbered item.

Reference herein to “one or more examples” means that one or morefeature, structure, or characteristic described in connection with theexample is included in at least one implementation. The phrase “one ormore examples” in various places in the specification may or may not bereferring to the same example.

As used herein, a system, apparatus, structure, article, element,component, or hardware “configured to” perform a specified function isindeed capable of performing the specified function without anyalteration, rather than merely having the potential to perform thespecified function after further modification. In other words, thesystem, apparatus, structure, article, element, component, or hardware“configured to” perform a specified function is specifically selected,created, implemented, utilized, programmed, and/or designed for thepurpose of performing the specified function. As used herein,“configured to” denotes existing characteristics of a system, apparatus,structure, article, element, component, or hardware that enable thesystem, apparatus, structure, article, element, component, or hardwareto perform the specified function without further modification. Forpurposes of this disclosure, a system, apparatus, structure, article,element, component, or hardware described as being “configured to”perform a particular function may additionally or alternatively bedescribed as being “adapted to” and/or as being “operative to” performthat function.

Illustrative, non-exhaustive examples of the subject matter, disclosedherein, are provided below.

Referring generally to FIGS. 1, 3A, and 3B and particularly to, e.g.,FIGS. 2A and 2B for illustrative purposes only and not by way oflimitation, the following portion of this paragraph delineates example 1of the subject matter, disclosed herein. According to example 1, method300 of configuring additive-manufacturing machine 100 that compriseschamber 102, platform 107, movable inside chamber 102 and comprisingbuild-plane surface 105, and laser 106, having laser focal plane 108within chamber 102, is described. Method 300 comprises steps of (block310) flowing gas 101 within chamber 102 in accordance with first set ofprocess parameters 161 and identifying a value of a flow characteristicof gas 101 at predetermined point 109 in laser focal plane 108 while(block 320) flowing gas 101 within chamber 102 in accordance with firstset of process parameters 161. Method 300 further comprises a step of(block 330) additively manufacturing test coupon 190 using laser 106while flowing gas 101 within chamber 102 in accordance with first set ofprocess parameters 161. Test coupon 190 has test-coupon peripheralsurface 191. Method 300 further comprises a step of (block 340)comparing a value of the physical property at predetermined location 192on or underneath test-coupon peripheral surface 191 to a desired valueof the physical property. Method 300 also comprises a step of (block350) flowing gas 101 within chamber 102 in accordance with second set ofprocess parameters 162, different from first set of process parameters161, when a difference between the value of the physical property atpredetermined location 192 on or underneath test-coupon peripheralsurface 191 and the desired value of the physical property is outside ofa predetermined range.

The value of the physical property at predetermined location 192 on orunderneath test-coupon peripheral surface 191 indicates whetheradditive-manufacturing machine 100 can be used for manufacturing actualproduction parts, e.g., when the difference (between the value of thephysical property at predetermined location 192 on or underneathtest-coupon peripheral surface 191 and the desired value of the physicalproperty) is within the predetermined range. In other words, the value(of the physical property at predetermined location 192 on or underneathtest-coupon peripheral surface 191) indicates the expected properties ofthese manufactured parts. At the same time, this value depends on theprocess parameters, used for additive manufacturing of test coupon 190.Specifically, this value depends on first set of process parameters 161used to flow gas 101 within chamber 102. As such, any changes to theseprocess parameters can change the value of the physical property atpredetermined location 192 on or underneath test-coupon peripheralsurface 191. This feedback is used to determine process parameters thatyield the desired value of the physical property, e.g., the one withinthe predetermined range. During this process of configuringadditive-manufacturing machine 100, process parameters can be changed(e.g., from first set of process parameters 161 to second set of processparameters 162) until the difference between the value of the physicalproperty at predetermined location 192 on or underneath test-couponperipheral surface 191 and the desired value of the physical property iswithin the predetermined range.

Various examples of test coupon 190 are contemplated. For example, testcoupon 190 can have a narrow neck (e.g., having a so-called “dog-bone”shape) when test coupon 190 is subjected to a tensile test. Test coupon190 can be formed from various materials, such as metal, plastic, and/orceramics. Test coupon 190 is formed, e.g., by selectively sintering apowder layer, positioned at laser focal plane 108 within chamber 102.Specifically, laser 106 produces a laser beam, which is directed to thepowder layer. Gas 101 is flown within chamber 102. (e.g., in accordancewith first set of process parameters 161 or second set of processparameters 162) to remove fumes and ensure that the laser path (e.g.,between laser 106 and laser focal plane 108) is unobstructed. As such,these process parameters can impact the sintering process and theproperties of test coupon 190 by removing the fumes from the laser path.

Gas 101 is flown using various components of additive-manufacturingmachine 100 as, e.g., is shown in FIG. 2A. For example, fan 118 directsgas 101 to inlet 112 and additional inlet 113, through which gas 101enters chamber 102. Gas 101 passes through chamber 102 and exits throughoutlet 114. In some examples, gas 101 is passed through filter 116 toremove any contaminants before being returned back into chamber 102.This recirculation of gas 101 through chamber 102 removes contaminantsand helps to keep the laser path unobstructed. The effectiveness of thisgas recirculation process depends on the flow characteristic of gas 101.The flow characteristic is identified at one or more specific locationswithin chamber 102, such as predetermined point 109 in laser focal plane108 while flowing gas 101 within chamber 102. Furthermore, the flowcharacteristic of gas 101 or, more specifically, the value of the flowcharacteristic of gas 101 depends on the process parameters (e.g., firstset of process parameters 161) within chamber 102.

Referring generally to FIGS. 1, 3A, and 3B and particularly to, e.g.,FIG. 2A for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 2 of the subjectmatter, disclosed herein. According to example 2, which encompassesexample 1, above, each of first set of process parameters 161 and secondset of process parameters 162 comprises at least one of a fan speed, afilter type, or an orientation of a flow curtain within chamber 102.

The flow characteristic of gas 101 or, more specifically, the value ofthe flow characteristic of gas 101 depends on the process parameters(e.g., first set of process parameters 161, second set of processparameters 162) within chamber 102. At the same time, the flowcharacteristic of gas 101 has an impact on the physical properties oftest coupon 190 or, more specifically, the physical property atpredetermined location 192 on or underneath test-coupon peripheralsurface 191. As such, these process parameters have an impact on thephysical property at predetermined location 192 on or underneathtest-coupon peripheral surface 191. Controlling each of these processparameters helps to achieve the desired physical property, e.g., whenthe difference between the value of the physical property atpredetermined location 192 on or underneath test-coupon peripheralsurface 191 and the desired value of the physical property is within thepredetermined range.

For example, a higher fan speed increases the speed, at which gas 101 isflown within chamber 102, and can help with faster and more efficientremoving contaminants from chamber 102. A higher fan speed can be used,e.g., when the contamination level within chamber 102 is otherwise highand interferes with the laser beam, as the laser beam passes from laser106 to laser focal plane 108. However, excessive fan speeds can causeturbulence, vortexes, and other undesirable phenomena, which can becaptured as the flow characteristic of gas 101. A filter type alsoimpacts the speed, at which gas 101 can be flown within chamber 102,e.g., how much restriction to the gas flow is presented by filter 116.However, a filter type also determines the amount and the type ofcontaminants, removed from gas 101 before gas 101 is reintroduced intochamber 102. In some examples, one or more flow curtains are used withinchamber 102 to redirect gas 110 within chamber 102, in addition to theinitial direction, provided by the inlets.

Referring generally to FIGS. 1, 3A, and 3B and particularly to, e.g.,FIGS. 2B, 2C, and 2E for illustrative purposes only and not by way oflimitation, the following portion of this paragraph delineates example 3of the subject matter, disclosed herein. According to example 3, whichencompasses example 1 or 2, above, the step of (block 320) identifyingthe value of flow characteristic of gas 101 at the predetermined pointin laser focal plane 108 comprises (block 322) determiningstatic-pressure values at multiple points in laser focal plane 108 and(block 324) analyzing the static-pressure values to determine the valueof flow characteristic of gas 101 at predetermined point 109 in laserfocal plane 108.

The static-pressure values at multiple points in laser focal plane 108are representative of the various flow characteristics of gas 101, suchas the direction of gas 101 in chamber 102 and the speed, at which gas101 travels through chamber 102. For example, the static-pressuredifference between two points can be used for these purposes. Thelocations of these points determine which flow characteristics of gas101 can be identified.

FIG. 2E illustrates multiple points (identified as reference-plateopenings 158 in reference plate 154 of flow-characterization system150). In some examples, the difference or, more generally, thevariations of the static-pressure values among different points in laserfocal plane 108 can be used to determine the value of flowcharacteristic of gas 101 at predetermined point 109 in laser focalplane 108. For example, two points, positioned along the X-axis, canhave different static-pressure values. This difference can be correlatedto the gas flow along the X-axis. In some examples, predetermined point109 in laser focal plane 108 coincides with one of the multiple pointsin laser focal plane 108, at which the static-pressure values areidentified. Alternatively, predetermined point 109 in laser focal plane108 is positioned between two or more of the multiple points in laserfocal plane 108.

Referring generally to FIGS. 1, 3A, and 3B and particularly to, e.g.,FIGS. 2A and 2B for illustrative purposes only and not by way oflimitation, the following portion of this paragraph delineates example 4of the subject matter, disclosed herein. According to example 4, whichencompasses example 3, above, the static-pressure values at the multiplepoints in laser focal plane 108 within chamber 102. are determined usingcomputational-fluid-dynamics analysis.

Computational-fluid-dynamics analysis enables the static-pressure valuesat the multiple points in laser focal plane 108 within chamber 102 to bedetermined without performing an actual test and using any test probe,thereby saving time and eliminating the need for test equipment.

In some examples, computational-fluid-dynamics analysis enables thestatic-pressure values to be determined at any location in laser focalplane 108 within chamber 102. Furthermore, in some examples,computational-fluid-dynamics analysis enables these locations to bechanged as needed, e.g., to provide a more specific correlation to thevalue of the physical property at predetermined location 192 on orunderneath test-coupon peripheral surface 191.

Referring generally to FIGS. 1, 3A, and 3B and particularly to, e.g.,FIGS. 2A and 2B for illustrative purposes only and not by way oflimitation, the following portion of this paragraph delineates example 5of the subject matter, disclosed herein. According to example 5, whichencompasses any one of examples 1 to 4, above, the flow characteristicof gas 101 is a linear flowrate of gas 101 at predetermined point 109 inlaser focal plane 108.

The linear flowrate of gas 101 at predetermined point 109 in laser focalplane 108 is an indication of how fast contaminants are being removedfrom chamber 102. Furthermore, the linear flowrate of gas 101 can impactthermal conditions during sintering, e.g., a higher flowrate,corresponding to more cooling. It should be noted that laser focal plane108 is where the sintering occurs during additive manufacturing.

In some examples, multiple linear flowrates of gas 101 are measuredwithin chamber 102, e.g., flowrates in different directions atpredetermined point 109 in laser focal plane 108 or flowrates atdifferent points, e.g., within laser focal plane 108 and/or away fromlaser focal plane 108.

Referring generally to FIGS. 1 and 3 and particularly to, e.g., FIG. 2Bfor illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 6 of the subjectmatter, disclosed herein. According to example 6, which encompasses anyone of examples 1 to 5, laser 106 is not operational during the step of(block 320) identifying the value of flow characteristic of gas 101.

With laser 106 not being operational, various metrology tools can bepositioned within chamber 102 to determine the flow characteristic ofgas 101 and without any risk of being damaged by laser 106. For example,flow-characterization system 150 can be placed on platform 107 ofadditive-manufacturing machine 100 to determine the flow characteristicof gas 101. It should be noted that platform 107 is in the direct lineof sight of laser 106.

The operation of laser 106 does not impact the flow characteristic ofgas 101 within chamber 102. As such, the value of the flowcharacteristic of gas 101 at predetermined point 109 in laser focalplane 108 while flowing gas 101 within chamber 102 in accordance withfirst set of process parameters 161 will be the same when laser 106 isoperational and when laser 106 is not operational.

Referring generally to FIGS. 1, 3A, and 3B and particularly to, e.g.,FIGS. 2B-2E for illustrative purposes only and not by way of limitation,the following portion of this paragraph delineates example 7 of thesubject matter, disclosed herein. According to example 7, whichencompasses any one of examples 1 to 6, the step of (block 320)identifying the value of flow characteristic of gas 101 at thepredetermined point in laser focal plane 108 is performed usingflow-characterization system 150, comprising pressure probes 152 andreference plate 154 that comprises datum surface 156 and reference-plateopenings 158, passing through datum surface 156. Datum surface 156 iscoplanar with laser focal plane 108 during the step of (block 320)identifying the value of flow characteristic of gas 101. Each ofpressure probes 152 is received by a respective one of reference-plateopenings 158 and is configured to monitor static pressure at datumsurface 156 of reference plate 154.

Flow-characterization system 150 is specifically configured foridentifying the value of flow characteristic of gas 101 at thepredetermined point in laser focal plane 108. The predetermined point inlaser focal plane 108 is determined by the position of reference-plateopenings 158 or, more specifically, by pressure probes 152, positionedin reference-plate openings 158. Pressure probes 152 obtain variouscharacteristics, which are combined to identify the value of flowcharacteristic of gas 101 at the predetermined point in laser focalplane 108.

Flow-characterization system 150 is positioned on platform 107 whenlaser 106 is not operational. As such, flow-characterization system 150is not damaged by laser 106 while identifying the value of flowcharacteristic of gas 101 at the predetermined point in laser focalplane 108. Flow-characterization system 150 comprises pressure probes152 for determining, e.g., static pressure at multiple locations.Flow-characterization system 150 also comprises reference plate 154 thatcomprises datum surface 156 and reference-plate openings 158, passingthrough datum surface 156. Datum surface 156 is coplanar with laserfocal plane 108 while identifying the value of flow characteristic ofgas 101. This positioning ensures that the flow characteristic of gas101 is determined at the predetermined point in laser focal plane 108(and not away from laser focal plane 108). Each of pressure probes 152is received by a respective one of reference-plate openings 158. Inother words, reference-plate openings 158 determine the locations ofpressure probes 152. Referring to FIG. 2C, in some examples, pressureprobes 152 are positioned below datum surface 156 to ensure that thestatic pressure (at datum surface 156 of reference plate 154) isaccurately measured and not impacted by the flow of gas 101 above datumsurface 156.

Referring generally to FIGS. 1, 3A, and 3B and particularly to, e.g.,FIG. 2B for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 8 of the subjectmatter, disclosed herein. According to example 8, which encompassesexample 7, above, method 300 further comprises, prior to the step of(block 320) identifying the value of the flow characteristic of gas 101at predetermined point 109 in laser focal plane 108, (block 312)positioning flow-characterization system 150 onto build-plane surface105 of platform 107. Method 300 also comprises (block 314) positioningplatform 107 so that datum surface 156 of reference plate 154 offlow-characterization system 150 is coplanar with laser focal plane 108.

Platform 107 provides the alignment of datum surface 156, relative tolaser focal plane 108 or, more specifically, ensures that datum surface156 is coplanar with laser focal plane 108. This alignment ensures thatthe flow characteristic of gas 101 is determined at the predeterminedpoint in laser focal plane 108 (and not away from laser focal plane108).

For example, flow-characterization system 150 has a height (extending inthe Z-direction). This height ensures that various external componentsof flow-characterization system 150 can be arranged and, if needed,accessed (e.g., while servicing flow-characterization system 150).Before positioning flow-characterization system 150, platform 107 can bepositioned such that a powder layer is at laser focal plane 108.However, this powder layer can be much thinner /shorter thanflow-characterization system 150. As such, if flow-characterizationsystem 150 is positioned on platform 107 without adjusting the height ofplatform 107, then datum surface 156 will be above laser focal plane108. Taking measurements at this location (above laser focal plane 108)are not useful, at least for some application. Platform 107 is thereforelowered until datum surface 156 is coplanar with laser focal plane 108.

Referring generally to FIGS. 1, 3A, and 3B and particularly to, e.g.,FIG. 2B for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 9 of the subjectmatter, disclosed herein. According to example 9, which encompassesexample 7 or 8, above, method 300 further comprises, after the step of(block 320) identifying the value of the flow characteristic of gas 101at the predetermined point in laser focal plane 108 and prior to thestep of (block 330) additively manufacturing test coupon 190, (block328) removing flow-characterization system 150 from platform 107 and(block 329) positioning platform 107 so that build-plane surface 105 ofplatform 107 is coplanar with laser focal plane 108.

Once the value of the flow characteristic of gas 101 is identified,flow-characterization system 150 is removed from platform 107. It shouldbe noted that during the operation of flow-characterization system 150,build-plane surface 105 of platform 107 is below laser focal plane 108,while datum surface 156 of reference plate 154 of flow-characterizationsystem 150 is coplanar with laser focal plane 108. Once the value of theflow characteristic of gas 101 is identified, additive-manufacturingmachine 100 needs to be returned to an operational state, in whichbuild-plane surface 105 of platform 107 is coplanar with laser focalplane 108. As such, platform 107 is raised until build-plane surface 105is coplanar with laser focal plane 108. In this state, build-planesurface 105 of platform 107 is ready to receive a precursor (e.g.,powder) for additive manufacturing.

In some examples, platform 107 is equipped with one or more linearactuators used for lowering and raising platform 107. Some examplesinclude, but are not limited to threaded rods, pneumatic cylinders,scotch yokes, and solenoids.

Referring generally to FIGS. 1, 3A, and 3B and particularly to, e.g.,FIGS. 2B-2D for illustrative purposes only and not by way of limitation,the following portion of this paragraph delineates example 10 of thesubject matter, disclosed herein. According to example 10, whichencompasses any one of examples 7 to 9, flow-characterization system 150further comprises extensible pressure probe 153, protruding above datumsurface 156 of reference plate 154. Method 300 further comprises a stepof (block 325) identifying a value of an additional flow characteristicof gas 101 at an additional predetermined point, spaced away from laserfocal plane 108, using extensible pressure probe 153.

The value of the additional flow characteristic of gas 101 at theadditional predetermined point, spaced away from laser focal plane 108,provides an additional characterization of the gas flow within chamber102. This value can be used together with the value of the physicalproperty at predetermined location 192 on or underneath test-couponperipheral surface 191 to provide a more comprehensive view of the gasflow within chamber 102.

For example, the value of the additional flow characteristic of gas 101at the additional predetermined point can be compared with the value ofthe flow characteristic of gas 101 at predetermined point 109, e.g., todetermine any variations of the flow characteristic along the Z-axis ofchamber 102. It should be noted that the laser beam travels from laser106 to focal plane 108 along the Z-axis of chamber 102. As such, thevalue of the additional flow characteristic of gas 101 at the additionalpredetermined point provides additional input.

Extensible pressure probe 153 can be supported using reference plate 154as, e.g., is shown in FIGS. 2C and 2D, or a wall of chamber 102 as,e.g., is shown in FIG. 2B. In some examples, inlet probe 157 is used toidentify the value of the additional flow characteristic of gas 101 atthe additional predetermined point, spaced away from laser focal plane108. This additional predetermined point can be positioned at one of thechamber inlets as, e.g., is schematically shown in FIG. 2B.

Referring generally to FIGS. 1, 3A, and 3B and particularly to, e.g.,FIGS. 2B-2D for illustrative purposes only and not by way of limitation,the following portion of this paragraph delineates example 11 of thesubject matter, disclosed herein. According to example 11, whichencompasses example 10, above, the step of (block 325) identifying thevalue of the additional flow characteristic of gas 101 at the additionalpredetermined point, spaced away from laser focal plane 108, usingextensible pressure probe 153 and the step of (block 320) identifyingthe value of the flow characteristic of gas 101 at predetermined point109 in laser focal plane 108 overlap in time.

A combination of the additional flow characteristic of gas 101 at theadditional predetermined point and the flow characteristic of gas 101 atpredetermined point 109 provide a more comprehensive analysis of theflow conditions within chamber 102 than either one of these flowcharacteristics on its own. The cumulative effect is achieved when thecorresponding values of these flow characteristics are obtained withinthe same timeframe. In other words, both values characterize the samegas flow condition within the chamber.

For example, identifying the value of the additional flow characteristicof gas 101 at the additional predetermined point and identifying thevalue of the flow characteristic of gas 101 at predetermined point 109can start and end at the same time. In other examples, the start timeand/or end time can be different. In other words, these twoidentification operations are staggered in time.

Referring generally to FIGS. 1, 3A, and 3B and particularly to, e.g.,FIGS. 2B-2D for illustrative purposes only and not by way of limitation,the following portion of this paragraph delineates example 12 of thesubject matter, disclosed herein. According to example 12, whichencompasses example 11, above, flow-characterization system 150 furthercomprises actuator 159, coupled to extensible pressure probe 153. Thestep of (block 325) identifying the value of the additional flowcharacteristic of gas 101 at the additional predetermined point, spacedaway from laser focal plane 108, using extensible pressure probe 153,comprises (block 326) moving extensible pressure probe 153 relative todatum surface 156 of reference plate 154 in a direction, perpendicularto datum surface 156 using actuator 159.

Actuator 159 enables the position of extensible pressure probe 153 to bechanged relative to datum surface 156, e.g., as schematically shown inFIGS. 2C and 2D. As such, actuator 159 controls the position of theadditional predetermined point relative to datum surface 156. Thisposition can be changed, using actuator 159, to obtain even more values,each corresponding to a different position of the additionalpredetermined point relative to datum surface 156 of reference plate154.

Various examples of actuator 159 are contemplated, such as motorizedthreaded rods, pneumatic cylinders, scotch yokes, and solenoids.Actuator 159 can be positioned within an enclosure offlow-characterization system 150 to prevent interference with the gasflow within chamber 102. For example, actuator 159 can be positionedbelow datum surface 156, relative to laser 106.

Referring generally to FIGS. 1, 3A, and 3B and particularly to, e.g.,FIGS. 2C and 2D for illustrative purposes only and not by way oflimitation, the following portion of this paragraph delineates example13 of the subject matter, disclosed herein. According to example 13,which encompasses example 11 or 12, above, method 300 further comprisesa step of (block 327) identifying, at additional predetermined points,values of additional flow characteristics of gas 101. At least one ofthe additional predetermined points is farther away from laser focalplane 108 than at least another one of the additional predeterminedpoints.

Measuring the flow characteristics of gas 101 at additional pointsprovides additional input, resulting in a more comprehensive analysis ofthe flow conditions within chamber 102. The laser beam travels fromlaser 106 to focal plane 108 along the Z-axis of chamber 102. As such,the gas flow at various distances away from laser focal plane 108 canimpact the passage of this laser beam. For example, contamination awayfrom laser focal plane 108 can impact the passage of the laser beam tofocal plane 108.

In some examples, these additional predetermined points are selectedbased on the height of chamber 102, vertical positions of the variousinlets and outlets into the chamber, the orientation of the inlets, andother factors.

Referring generally to FIGS. 1, 3A, and 3B and particularly to, e.g.,FIGS. 2C and 2D for illustrative purposes only and not by way oflimitation, the following portion of this paragraph delineates example14 of the subject matter, disclosed herein. According to example 14,which encompasses example 13, above, the step of (block 327)identifying, at the additional predetermined points, the additional flowcharacteristics of gas 101 is performed using extensible pressure probe153.

Extensible pressure probe 153 can change the measurement positionrelative to datum surface 156 of reference plate 154 and also relativeto laser focal plane 108. As such, extensible pressure probe 153 canobtain multiple measurements within chamber 102, which provide a morecomprehensive analysis of the flow conditions within chamber 102.

In some examples, these additional predetermined points are selectedbased on the height of chamber 102, vertical positions of the variousinlets and outlets into the chamber, the orientation of the inlets, andother factors.

Referring generally to FIGS. 1, 3A, and 3B and particularly to, e.g.,FIGS. 2A and 2B for illustrative purposes only and not by way oflimitation, the following portion of this paragraph delineates example15 of the subject matter, disclosed herein. According to example 15,which encompasses any one of examples 1 to 14, second set of processparameters 162 is determined based on the value of the physical propertyat predetermined location 192 on or underneath test-coupon peripheralsurface 191 and further based on first set of process parameters 161.

Test coupon 190 or, more specifically, the value of the physicalproperty at predetermined location 192 on or underneath test-couponperipheral surface 191 is used as feedback for determining second set ofprocess parameters 162. This value indicates how first set of processparameters 161 needs to be adjusted, producing second set of processparameters 162. The adjustment level can depend, for example, on thedifference between the value of the physical property at predeterminedlocation 192 on or underneath test-coupon peripheral surface 191 and thedesired value of the physical property.

Referring generally to FIGS. 1, 3A, and 3B and particularly to, e.g.,FIGS. 2A and 2B for illustrative purposes only and not by way oflimitation, the following portion of this paragraph delineates example16 of the subject matter, disclosed herein. According to example 16,which encompasses any one of examples 1 to 14, second set of processparameters 162 is determined based on the value of the flowcharacteristic of gas 101 at predetermined point 109 in laser focalplane 108 and further based on the value of the physical property atpredetermined location 192 on or underneath test-coupon peripheralsurface 191.

The value of the flow characteristic of gas 101 at predetermined point109 in laser focal plane 108 provides additional feedback fordetermining second set of process parameters 162. For example, thisvalue can be compared to a reference value of the flow characteristic ofgas 101 at predetermined point 109 in laser focal plane 108. Thereference value can be obtained during the qualification and validationof additive-manufacturing machine 100.

Referring generally to FIGS. 1, 3A, and 3B and particularly to, e.g.,FIGS. 2A and 2B for illustrative purposes only and not by way oflimitation, the following portion of this paragraph delineates example17 of the subject matter, disclosed herein. According to example 17,which encompasses any one of examples 1 to 16, method 300 furthercomprises a step of (block 360) identifying a value of the flowcharacteristic of gas 101 at predetermined point 109 in laser focalplane 108 while flowing gas 101 within chamber 102 in accordance withsecond set of process parameters 162. Method 300 also comprises a stepof (block 362) additively manufacturing second test coupon 195 usinglaser 106 while flowing gas 101 within chamber 102 in accordance withsecond set of process parameters 162. Second test coupon 195 hassecond-test-coupon peripheral surface 196. Method 300 additionallycomprises a step of (block 364) comparing a value of the physicalproperty at second predetermined location 197 on or underneathsecond-test-coupon peripheral surface 196 to the desired value of thephysical property. Method 300 also comprises a step of (block 366)flowing gas 101 within chamber 102 in accordance with a third set ofprocess parameters 163, different from first set of process parameters161 and from second set of process parameters 162, when a differencebetween the value of the physical property at second predeterminedlocation 197 on or underneath second-test-coupon peripheral surface 196and the desired value of the physical property is outside of thepredetermined range.

Second test coupon 195 provides feedback about second set of processparameters 162, which is additional input. Specifically, second testcoupon 195 provides feedback if the changes from first set of processparameters 161 (used to additively manufactured test coupon 190) tosecond set of process parameters 162 (used to additively manufacturedsecond test coupon 195) help to get closer to the desired value of thephysical property. Second set of process parameters 162 are selected toimprove the value of the physical property at predetermined location 192on or underneath test-coupon peripheral surface 191, e.g., to get withinthe desired range or at least close to this range.

In some examples, the desired value is achieved and no further changesto process parameters are needed. In other words, second set of processparameters 162 can be used for additive manufacturing without furthertesting and configuring additive-manufacturing machine 100.Alternatively, when the desired value is not achieved, the differencesbetween the value of the physical property at second predeterminedlocation 197 on or underneath second-test-coupon peripheral surface 196and the desired value of the physical property are evaluated for bothtest coupon 190 and second test coupon 195. For example, this differencecan be greater for test coupon 190 than for second test coupon 195. Inthis case, second set of process parameters 162 is more favorable thanfirst set of process parameters 161. More specifically, the change fromfirst set of process parameters 161 to second set of process parameters162 was in the right direction. Alternatively, this difference can besmaller for test coupon 190 than for second test coupon 195. In thiscase, second set of process parameters 162 is less favorable than firstset of process parameters 161, and the process can return to first setof process parameters 161 or change in another direction.

In some examples, this process of additively manufacturing test couponsis repeated until the difference between the value of the physicalproperty at second predetermined location 197 on or underneath theperipheral surface of the latest test coupon and the desired value ofthe physical property is within the predetermined range.

Referring generally to FIGS. 1, 3A, and 3B and particularly to, e.g.,FIGS. 2A and 2B for illustrative purposes only and not by way oflimitation, the following portion of this paragraph delineates example18 of the subject matter, disclosed herein. According to example 18,which encompasses any one of examples 1 to 17, method 300 furthercomprises (block 370) selecting first set of process parameters 161 foroperating additive-manufacturing machine 100 when the difference betweenthe value of the physical property at predetermined location 192 on orunderneath test-coupon peripheral surface 191 and the desired value ofthe physical property is within the predetermined range.

The difference between the value of the physical property atpredetermined location 192 on or underneath test-coupon peripheralsurface 191 and the desired value of the physical property indicates iffirst set of process parameters 161 (used to additively manufacturedtest coupon 190) can be used for operating additive-manufacturingmachine 100. In other words, the physical property at predeterminedlocation 192 on or underneath test-coupon peripheral surface 191provides feedback about the process parameters and whether theseparameters can be used for operating additive-manufacturing machine 100.When the difference is within the predetermined range for first set ofprocess parameters 161, first set of process parameters 161 can beselected for operating additive-manufacturing machine 100.

It should be noted that, in some examples, the process parameters can bechanged one or more times (e.g., from first set of process parameters161 to second set of process parameters 162, from second set of processparameters 162 to third set of process parameters 163) before thedifference between the value of the physical property and the desiredvalue of the physical property is within the predetermined range. Oncethis difference is within the predetermined range, the latest set ofprocess parameters is used for operating additive-manufacturing machine100.

Referring generally to FIGS. 1, 3A, and 3B and particularly to, e.g.,FIG. 2A for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 19 of the subjectmatter, disclosed herein. According to example 19, which encompassesexample 18, above, method 300 further comprises (block 380) selectingthe value of the flow characteristic of gas 101 at the predeterminedpoint in laser focal plane 108 as a reference test parameter foroperating additive-manufacturing machine 100.

When the difference between the value of the physical property atpredetermined location 192 on or underneath test-coupon peripheralsurface 191 and the desired value of the physical property is within thepredetermined range for first set of process parameters 161, first setof process parameters 161 can be selected for operatingadditive-manufacturing machine 100. First set of process parameters 161are controlled externally and, in some examples, are not able to accountfor some internal variations of additive-manufacturing machine 100(e.g., filter cleanness). At the same time, first set of processparameters 161 was previously used to flow gas 101 within chamber 102and identifying the value of the flow characteristic of gas 101 at thepredetermined point in laser focal plane 108. The value of the flowcharacteristic of gas 101 accounts for various internal variations ofadditive-manufacturing machine 100 (in addition to changes to first setof process parameters 161). As such, the value of the flowcharacteristic of gas 101 can be used for internal control and, moregenerally, as a reference test parameter for operatingadditive-manufacturing machine 100.

For example, flow-characterization system 150 can be periodicallyinstalled into additive-manufacturing machine 100, and gas 101 is flownwithin chamber 102 in accordance with first set of process parameters161. Flow-characterization system 150 determined the value of the flowcharacteristic of gas 101 at the predetermined point in laser focalplane 108 and this value can be compared to the reference test parameterto ensure that no changes to additive-manufacturing machine 100 haveoccurred and that additive-manufacturing machine 100 can continue tooperate.

Referring generally to FIGS. 1, 3A, and 3B and particularly to, e.g.,FIG. 2A for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 20 of the subjectmatter, disclosed herein. According to example 20, which encompassesexample 1, above, the step of (block 330) additively manufacturing testcoupon 190 comprises (block 332) placing powder layer 199 ontobuild-plane surface 105 of platform 107 and heating powder layer withlaser 106 to locally melt powder layer 199.

When powder layer 199 locally melts and later cools, a monolithic bodyof test coupon 190 is formed. The local melting is provided by laser106, which can be focused on any portion of powder layer 199 therebydetermining the shape of test coupon 190. This local melting determinesthe shape of test coupon 190. Portions of powder layer 199 that have notbeen melted are removed (and rearranged). The process is repeated tobuild up test coupon 190.

Referring generally to FIGS. 1 and 4 and particularly to, e.g., FIGS.2B-2E for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 21 of the subjectmatter, disclosed herein. According to example 21, method 400 ofconfiguring additive-manufacturing machine 100 that comprises chamber102, platform 107, movable inside chamber 102 and comprising build-planesurface 105, and laser 106, having laser focal plane 108 within chamber102, is described. Method 400 comprises a step of (block 410) flowinggas 101 within chamber 102 in accordance with first set of processparameters 161. Method 400 also comprises a step of (block 420)identifying a value of a flow characteristic of gas 101 at apredetermined point in laser focal plane 108 while flowing gas 101within chamber 102 in accordance with first set of process parameters161. Method 400 further comprises a step of (block 430) simulating thestep of flowing gas 101 within chamber 102 based on the value of flowcharacteristic of gas 101 at the predetermined point in laser focalplane 108 so that a value of a simulated-flow characteristic of gas 101at a predetermined point away from laser focal plane 108 is identified.Method 400 additionally comprises a step of (block 440) comparing thevalue of the simulated-flow characteristic of gas 101 at thepredetermined point away from laser focal plane 108 to a desired valueof simulated-flow characteristic. Method 400 also comprises a step of(block 450) flowing gas 101 within chamber 102 in accordance with secondset of process parameters 162, different from first set of processparameters 161, when a difference between the value of thesimulated-flow characteristic of gas 101 at the predetermined point awayfrom laser focal plane 108 and the desired value of the simulated-flowcharacteristic is outside of a predetermined range.

Simulating the step of flowing gas 101 within chamber 102 based on thevalue of flow characteristic of gas 101 at the predetermined point inlaser focal plane 108 can be used instead of additively manufacturing atest coupon (e.g., to expedite the system qualification) or in additionto additively manufacturing a test coupon (e.g., to provide additionalfeedback). The value of flow characteristic of gas 101 is used as aninput to this simulation. For example, the flow characteristic of gas101 can be a linear speed of gas 101 as gas 101 flows through chamber102. This value depends on first set of process parameters 161 used toflow gas 101 within chamber 102. As such, any changes to these processparameters can result in changes to the value of simulated-flowcharacteristic of gas 101. This feedback is used to determine processparameters that yield the desired value of the simulated-flowcharacteristic, e.g., the one within the predetermined range. Processparameters can be changed (e.g., from first set of process parameters161 to second set of process parameters 162) until the differencebetween the value of the simulated-flow characteristic and the desiredvalue of the physical property is within the predetermined range.

Gas 101 is flown using various components of additive-manufacturingmachine 100 as, e.g., is shown in FIG. 2B. For example, fan 118 directsgas 101 to inlet 112 and additional inlet 113, through which gas 101enters chamber 102. Gas 101 passes through chamber 102 and exits throughoutlet 114. In some examples, gas 101 is passed through filter 116 toremove any contaminants before being returned back into chamber 102.This recirculation of gas 101 through chamber 102 removes contaminantsand helps to keep the laser path unobstructed. The effectiveness of thisgas recirculation process depends on the flow characteristic of gas 101.The flow characteristic is identified at one or more specific locationswithin chamber 102, such as predetermined point 109 in laser focal plane108 while flowing gas 101 within chamber 102. Furthermore, the flowcharacteristic of gas 101 or, more specifically, the value of the flowcharacteristic of gas 101, depends on the process parameters (e.g.,first set of process parameters 161) within chamber 102.

Referring generally to FIGS. 1 and 4 and particularly to, e.g., FIGS.2B-2E for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 22 of the subjectmatter, disclosed herein. According to example 22, which encompassesexample 21, above, the step of (block 430) simulating the step offlowing gas 101 within chamber 102 based on the value of the flowcharacteristic of gas 101 at the predetermined point in laser focalplane 108 within chamber 102 comprises performingcomputational-fluid-dynamics analysis.

The computational-fluid-dynamics analysis provides a fast and efficientway of determining the value of the simulated-flow characteristic of gas101 at the predetermined point away from laser focal plane 108. Thecomputational-fluid-dynamics analysis is performed using gas flowcharacteristics, identified earlier, as inputs (e.g., as a part ofboundary conditions). In some examples, a computer-aided design (CAD) ofchamber 102 and various components of additive-manufacturing machine100, which are positioned inside chamber 102, are provided as inputs tothe computational-fluid-dynamics analysis. Chamber 102. or, morespecifically, the volume, occupied by gas 101, is divided into discretecells. Boundary conditions are defined using, e.g., the value of theflow characteristic of gas 101 at the predetermined point in laser focalplane 108 within chamber 102. The gas flow can be viewed as asteady-state system, and various fluid dynamics equations are solvediteratively for this system.

Referring generally to FIGS. 1 and 4 and particularly to, e.g., FIGS.2B-2E for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 23 of the subjectmatter, disclosed herein. According to example 23, which encompassesexample 21 or 22, above, each of first set of process parameters 161 andsecond set of process parameters 162 comprises at least one of a fanspeed, a filter type, or an orientation of a flow curtain within chamber102.

The flow characteristic of gas 101 or, more specifically, the value ofthe flow characteristic of gas 101, depends on the process parameters(e.g., first set of process parameters 161, second set of processparameters 162) within chamber 102. At the same time, the flowcharacteristic of gas 101 has an impact on the physical properties oftest coupon 190 or, more specifically, the physical property atpredetermined location 192 on or underneath test-coupon peripheralsurface 191. As such, these process parameters have an impact on thephysical property at predetermined location 192 on or underneathtest-coupon peripheral surface 191. Controlling each of these processparameters helps to achieve the desired physical property, e.g., whenthe difference between the value of the physical property atpredetermined location 192 on or underneath test-coupon peripheralsurface 191 and the desired value of the physical property is within thepredetermined range.

For example, a higher fan speed increases the speed, at which gas 101 isflown within chamber 102, and can help with faster and more efficientremoval of contaminants from chamber 102. A higher fan speed can beused, e.g., when the contamination level within chamber 102 is otherwisehigh and interferes with the laser beam as the laser beam passes fromlaser 106 to laser focal plane 108. However, excessive fan speeds cancause turbulence, vortexes, and other undesirable phenomena, which canbe captured as the flow characteristic of gas 101. A filter type alsoimpacts the speed, at which gas 101 can be flown within chamber 102,e.g., how much restriction to the gas flow is presented by filter 116.However, a filter type also determines the amount and the type ofcontaminants, removed from gas 101 before gas 101 is reintroduced intochamber 102. In some examples, one or more flow curtains are used withinchamber 102 to redirect gas 110 within chamber 102, in addition to theinitial direction, provided by the inlets.

Referring generally to FIGS. 1 and 4 and particularly to, e.g., FIGS.2B-2E for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 24 of the subjectmatter, disclosed herein. According to example 24, which encompasses anyone of examples 21 to 23, above, the step of (block 420) identifying thevalue of flow characteristic of gas 101 at the predetermined point inlaser focal plane 108 comprises (block 422) determining static-pressurevalues at multiple points in laser focal plane 108 and (block 424)analyzing the static-pressure values to determine the value of flowcharacteristic of gas 101 at predetermined point 109 in laser focalplane 108.

The static-pressure values at multiple points in laser focal plane 108are representative of the various flow characteristics of gas 101, suchas the direction of gas 101 in chamber 102 and the speed, at which gas101 travels through chamber 102. For example, the static-pressuredifference between two points can be used for these purposes. Thelocations of these points determine which flow characteristics of gas101 can be identified.

FIG. 2E illustrates multiple points (identified as reference-plateopenings 158 in reference plate 154 of flow-characterization system150). In some examples, the difference or, more generally, thevariations of the static-pressure values among different points in laserfocal plane 108 can be used to determine the value of flowcharacteristic of gas 101 at predetermined point 109 in laser focalplane 108. For example, two points, positioned along the X-axis, canhave different static-pressure values. This difference can be correlatedto the gas flow along the X-axis. In some examples, predetermined point109 in laser focal plane 108 coincides with one of the multiple pointsin laser focal plane 108, at which the static-pressure values areidentified. Alternatively, predetermined point 109 in laser focal plane108 is positioned between two or more of the multiple points in laserfocal plane 108.

Referring generally to FIGS. 1 and 4 and particularly to, e.g., FIG. 2Bfor illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 25 of the subjectmatter, disclosed herein. According to example 25, which encompassesexample 24, above, the static-pressure values at the multiple points inlaser focal plane 108 within chamber 102 are determined usingcomputational-fluid-dynamics analysis.

Computational-fluid-dynamics analysis enables the static-pressure valuesat the multiple points in laser focal plane 108 within chamber 102 to bedetermined without performing an actual test and using any test probes,thereby saving time and eliminating the need for test equipment.

In some examples, computational-fluid-dynamics analysis enables thestatic-pressure values at any locations in laser focal plane 108 withinchamber 102 to be determined. Furthermore, in some examples,computational-fluid-dynamics analysis enables these locations to bechanged as needed, e.g., to provide a more specific correlation to thevalue of the physical property at predetermined location 192 on orunderneath test-coupon peripheral surface 191.

Referring generally to FIGS. 1 and 4 and particularly to, e.g., FIGS.2B-2E for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 26 of the subjectmatter, disclosed herein. According to example 26, which encompasses anyone of examples 21 to 25, above, the flow characteristic of gas 101 is alinear flowrate of gas 101 at predetermined point 109 in laser focalplane 108.

The linear flowrate of gas 101 at predetermined point 109 in laser focalplane 108 is an indication of how fast contaminants are being removedfrom chamber 102. Furthermore, the linear flowrate of gas 101 can impactthermal conditions during sintering, e.g., a higher flowratecorresponding to more cooling. It should be noted that laser focal plane108 is where the sintering occurs during additive manufacturing.

In some examples, multiple linear flowrates of gas 101 are measuredwithin chamber 102, e.g., flowrates in different directions atpredetermined point 109 in laser focal plane 108 or flowrates atdifferent points, e.g., within laser focal plane 108 and/or away fromlaser focal plane 108.

Referring generally to FIGS. 1 and 4 and particularly to, e.g., FIGS.2B-2E for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 27 of the subjectmatter, disclosed herein. According to example 27, which encompasses anyone of examples 21 to 26, above, laser 106 is not operational during thestep of (block 420) identifying the value of flow characteristic of gas101.

With laser 106 not being operational, various metrology tools can bepositioned within chamber 102 to determine the flow characteristic ofgas 101 and without any risk of being damaged by laser 106. For example,flow-characterization system 150 can be placed on platform 107 ofadditive-manufacturing machine 100 to determine the flow characteristicof gas 101. It should be noted that platform 107 is in the direct lineof sight of laser 106.

The operation of laser 106 does not impact the flow characteristic ofgas 101 within chamber 102. As such, the value of the flowcharacteristic of gas 101 at predetermined point 109 in laser focalplane 108, while flowing the gas 101 within chamber 102 in accordancewith first set of process parameters 161, will be the same when laser106 is operational and when laser 106 is not operational.

Referring generally to FIGS. 1 and 4 and particularly to, e.g., FIGS.2B-2E for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 28 of the subjectmatter, disclosed herein. According to example 28, which encompasses anyone of examples 21 to 27, above, the step of (block 420) identifying thevalue of flow characteristic of gas 101 at the predetermined point inlaser focal plane 108 is performed using flow-characterization system150, comprising pressure probes 152 and reference plate 154 thatcomprises datum surface 156 and reference-plate openings 158, passingthrough datum surface 156. Datum surface 156 is coplanar with laserfocal plane 108 during the step of (block 420) identifying the value offlow characteristic of gas 101. Each of pressure probes 152 is receivedby a respective one of reference-plate openings 158 and is configured tomonitor static pressure at datum surface 156 of reference plate 154.

Flow-characterization system 150 is specifically configured foridentifying the value of flow characteristic of gas 101 at thepredetermined point in laser focal plane 108. The predetermined point inlaser focal plane 108 is determined by the position of reference-plateopenings 158 or, more specifically, by pressure probes 152 positioned inreference-plate openings 158. Pressure probes 152 obtained variouscharacteristics which are combined to identify the value of flowcharacteristic of gas 101 at the predetermined point in laser focalplane 108.

Flow-characterization system 150 is positioned onto platform 107 whenlaser 106 is not operational. As such, flow-characterization system 150is not damaged by laser 106 while identifying the value of flowcharacteristic of gas 101 at the predetermined point in laser focalplane 108. Flow-characterization system 150 comprises pressure probes152 for determining, e.g., static pressure at multiple locations.Flow-characterization system 150 also comprises reference plate 154 thatcomprises datum surface 156 and reference-plate openings 158, passingthrough datum surface 156. Datum surface 156 is coplanar with laserfocal plane 108 during the step of identifying the value of flowcharacteristic of gas 101. This positioning ensures that the flowcharacteristic of gas 101 is determined at the predetermined point inlaser focal plane 108 (and not away from laser focal plane 108). Each ofpressure probes 152 is received by a respective one of reference-plateopenings 158. In other words, reference-plate openings 158 determine thelocation of pressure probes 152. Referring to FIG. 2C, in some examples,pressure probes 152 are positioned below datum surface 156 to ensurethat the static pressure (at datum surface 156 of reference plate 154)is accurately measured.

Referring generally to FIGS. 1 and 4 and particularly to, e.g., FIG. 2Bfor illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 29 of the subjectmatter, disclosed herein. According to example 29, which encompassesexample 28, above, method 400 further comprises, prior to the step of(block 420) identifying the value of flow characteristic of gas 101 atpredetermined point 109 in laser focal plane 108, (block 412)positioning flow-characterization system 150 onto build-plane surface105 of platform 107. Method 400 also comprises (block 414) positioningplatform 107 so that datum surface 156 of reference plate 154 offlow-characterization system 150 is coplanar with laser focal plane 108.

Platform 107 provides the alignment of datum surface 156, relative tolaser focal plane 108 or, more specifically, ensures that datum surface156 is coplanar with laser focal plane 108. This alignment ensures thatthe flow characteristic of gas 101 is determined at the predeterminedpoint in laser focal plane 108 (and not away from laser focal plane108).

For example, flow-characterization system 150 has a height (extending inthe Z-direction). This height ensures that various external componentsof flow-characterization system 150 can be arranged and, if needed,accessed (e.g., while servicing flow-characterization system 150).Before positioning flow-characterization system 150, platform 107 can bepositioned such that a powder layer is at laser focal plane 108.However, this powder layer can be much thinner/shorter thanflow-characterization system 150. As such, if flow-characterizationsystem 150 is positioned on platform 107 without adjusting the height ofplatform 107, then datum surface 156 will be above laser focal plane108. Taking measurements at this location (above laser focal plane 108)are not useful, at least for some application. Platform 107 is thereforelowered until datum surface 156 is coplanar with laser focal plane 108.

Referring generally to FIGS. 1 and 4 and particularly to, e.g., FIG. 2Bfor illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 30 of the subjectmatter, disclosed herein. According to example 30, which encompassesexample 28 or 29, above, method 400 further comprises, after the step of(block 420) identifying the value of the flow characteristic of gas 101at the predetermined point in laser focal plane 108, (block 428)removing flow-characterization system 150 from platform 107 and (block429) positioning platform 107 so that build-plane surface 105 ofplatform 107 is coplanar with laser focal plane 108.

Once the value of the flow characteristic of gas 101 is identified,flow-characterization system 150 is removed from platform 107. It shouldbe noted that during the operation of flow-characterization system 150,build-plane surface 105 of platform 107 is below laser focal plane 108.Instead, datum surface 156 of reference plate 154 offlow-characterization system 150 is coplanar with laser focal plane 108.Additive-manufacturing machine 100 needs to be returned to anoperational state, in which build-plane surface 105 of platform 107 iscoplanar with laser focal plane 108, which is achieved by raisingplatform 107 until build-plane surface 105 is coplanar with laser focalplane 108. In this state, build-plane surface 105 of platform 107 isready to receive a precursor (e.g., powder) for additive manufacturing.

In some examples, platform 107 is equipped with one or more linearactuators used for lowering and raising platform 107. Some examplesinclude, but are not limited to threaded rods, pneumatic cylinders,scotch yokes, and solenoids.

Referring generally to FIGS. 1 and 4 and particularly to, e.g., FIGS.2B-2D for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 31 of the subjectmatter, disclosed herein. According to example 31, which encompasses anyone of examples 28 to 30, flow-characterization system 150 furthercomprises extensible pressure probe 153, protruding above datum surface156 of reference plate 154. Method 400 further comprises a step of(block 425) identifying a value of an additional flow characteristic ofgas 101 at an additional predetermined point, spaced away from laserfocal plane 108, using extensible pressure probe 153.

The value of the additional flow characteristic of gas 101 at theadditional predetermined point, spaced away from laser focal plane 108,provides an additional characterization of the gas flow within chamber102. This value can be used together with the value of the physicalproperty at predetermined location 192 on or underneath test-couponperipheral surface 191 to provide a more comprehensive view of the gasflow within chamber 102.

For example, the value of the additional flow characteristic of gas 101at the additional predetermined point can be compared with the value ofthe flow characteristic of gas 101 at predetermined point 109, e.g., todetermine any variations of the flow characteristic along the Z-axis ofchamber 102. It should be noted that the laser beam travels from laser106 to focal plane 108 along the Z-axis of chamber 102. As such, thevalue of the additional flow characteristic of gas 101 at the additionalpredetermined point provides additional input.

Extensible pressure probe 153 can be supported using reference plate 154as, e.g., is shown in FIGS. 2C and 2D. In some examples, inlet probe 157is used to identify the value of the additional flow characteristic ofgas 101 at the additional predetermined point, spaced away from laserfocal plane 108. This additional predetermined point can be positionedat one of the chamber inlets as, e.g., is schematically shown in FIG.2B.

Referring generally to FIGS. 1 and 4 and particularly to, e.g., FIGS.2B-2D for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 32 of the subjectmatter, disclosed herein. According to example 32, which encompassesexample 31, above, the step of (block 425) identifying the value of theadditional flow characteristic of gas 101 at the additionalpredetermined point, spaced away from laser focal plane 108, usingextensible pressure probe 153, and the step of (block 420) identifyingthe value of the flow characteristic of gas 101 at predetermined point109 in laser focal plane 108 overlap in time.

A combination of the additional flow characteristic of gas 101 at theadditional predetermined point and the flow characteristic of gas 101 atpredetermined point 109 provide a more comprehensive analysis of theflow conditions within chamber 102 than either one of these flowcharacteristics on its own. The cumulative effect is achieved when thecorresponding values of these flow characteristics are obtained withinthe same timeframe. In other words, both values characterize the samegas flow condition within the chamber.

For example, identifying the value of the additional flow characteristicof gas 101 at the additional predetermined point and identifying thevalue of the flow characteristic of gas 101 at predetermined point 109can start and end at the same time. In other examples, the start timeand/or end time can be different. In other words, these twoidentification operations are staggered in time.

Referring generally to FIGS. 1 and 4 and particularly to, e.g., FIGS.2B-2D for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 33 of the subjectmatter, disclosed herein. According to example 33, which encompassesexample 31, above, flow-characterization system 150 further comprisesactuator 159, coupled to extensible pressure probe 153. The step of(block 425) identifying the value of the additional flow characteristicof gas 101 at the additional predetermined point, spaced away from laserfocal plane 108, using extensible pressure probe 153, comprises (block426) moving extensible pressure probe 153 relative to datum surface 156of reference plate 154 in a direction, perpendicular to datum surface156 using actuator 159.

Actuator 159 enables the position of extensible pressure probe 153 to bechanged relative to datum surface 156, e.g., as schematically shown inFIGS. 2C and 2D. As such, actuator 159 controls the position of theadditional predetermined point relative to datum surface 156. Thisposition can be changed, using actuator 159, to obtain even more values,each corresponding to a different position of the additionalpredetermined point relative to datum surface 156 of reference plate154.

Various examples of actuator 159 are contemplated, such as motorizedthreaded rods, pneumatic cylinders, scotch yokes, and solenoids.Actuator 159 can be positioned within an enclosure offlow-characterization system 150 to prevent interference with the gasflow within chamber 102. For example, actuator 159 can be positionedbelow datum surface 156, relative to laser 106.

Referring generally to FIGS. 1 and 4 and particularly to, e.g., FIGS. 2Cand 2D for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 34 of the subjectmatter, disclosed herein. According to example 34, which encompassesexample 33, above, method 300 further comprises a step of (block 427)identifying, at additional predetermined points, values of additionalflow characteristics of gas 101. At least one of the additionalpredetermined points is farther away from laser focal plane 108 than atleast another one of the additional predetermined points.

Measuring the flow characteristics of gas 101 at additional pointsprovides additional input, resulting in a more comprehensive analysis ofthe flow conditions within chamber 102. The laser beam travels fromlaser 106 to focal plane 108 along the Z-axis of chamber 102. As such,the gas flow at various distances away from laser focal plane 108 canimpact the passage of the laser beam. For example, the contaminationaway from laser focal plane 108 can impact the passage of the laser beamto focal plane 108.

In some examples, these additional predetermined points are selectedbased on the height of chamber 102, vertical positions of the variousinlets and outlets into the chamber, the orientation of the inlets, andother factors.

Referring generally to FIGS. 1 and 4 and particularly to, e.g., FIGS. 2Cand 2D for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 35 of the subjectmatter, disclosed herein. According to example 35, which encompassesexample 34, above, the step of (block 427) identifying, at theadditional predetermined points, the values of the additional flowcharacteristics of gas 101 is performed using extensible pressure probe153.

Extensible pressure probe 153 can change the measurement positionrelative to datum surface 156 of reference plate 154 and also relativeto laser focal plane 108. As such, extensible pressure probe 153 canobtain multiple measurements within chamber 102, which provide a morecomprehensive analysis of the flow conditions within chamber 102.

In some examples, these additional predetermined points are selectedbased on the height of chamber 102, vertical positions of the variousinlets and outlets into the chamber, the orientation of the inlets, andother factors.

Referring generally to FIGS. 1 and 4 and particularly to, e.g., FIG. 2Bfor illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 36 of the subjectmatter, disclosed herein. According to example 36, which encompasses anyone of examples 21 to 35, second set of process parameters 162 isdetermined based on the value of the simulated-flow characteristic ofgas 101 at the predetermined point away from laser focal plane 108 andfurther based on first set of process parameters 161.

The value of the simulated-flow characteristic of gas 101 at tjepredetermined point away from laser focal plane 108 is used as feedbackfor determining second set of process parameters 162. This valueindicates how first set of process parameters 161 needs to be adjusted,producing second set of process parameters 162. The adjustment level candepend, for example, on the difference between the value of thesimulated-flow characteristic of gas 101 at tje predetermined point awayfrom laser focal plane 108 and the desired value of the simulated-flowcharacteristic.

Referring generally to FIGS. 1 and 4 and particularly to, e.g., FIG. 2Bfor illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 37 of the subjectmatter, disclosed herein. According to example 37, which encompasses anyone of examples 21 to 35, second set of process parameters 162 isdetermined based on the value of flow characteristic of gas 101 atpredetermined point 109 in laser focal plane 108 and further based onthe value of the simulated-flow characteristic of gas 101 at thepredetermined point away from laser focal plane 108.

The value of the flow characteristic of gas 101 at predetermined point109 in laser focal plane 108 and the value of the simulated-flowcharacteristic of gas 101 at the predetermined point away from laserfocal plane 108 provides additional feedback for determining second setof process parameters 162. For example, these values can be compared tothe corresponding reference values. These reference values can beobtained during the qualification and validation ofadditive-manufacturing machine 100.

Referring generally to FIGS. 1 and 4 and particularly to, e.g., FIG. 2Bfor illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 38 of the subjectmatter, disclosed herein. According to example 38, which encompasses anyone of examples 21 to 37, method 300 further comprises (block 460)selecting the first set of process parameters 161 for operatingadditive-manufacturing machine 100 when the difference between the valueof simulated-flow characteristic of gas 101 at the predetermined pointaway from laser focal plane 108 and the desired value of thesimulated-flow characteristic is within the predetermined range.

The difference between the value of the simulated-flow characteristic ofgas 101 at the predetermined point away from laser focal plane 108 andthe desired value of the simulated-flow characteristic is within thepredetermined range indicates when process parameters can be used foroperating additive-manufacturing machine 100. In other words, the valueof simulated-flow characteristic provides feedback about the processparameters and whether these parameters can be used for operatingadditive-manufacturing machine 100. When the difference is within thepredetermined range for first set of process parameters 161, first setof process parameters 161 can be selected for operatingadditive-manufacturing machine 100.

Referring generally to FIGS. 1 and 4 and particularly to, e.g., FIG. 2Afor illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 39 of the subjectmatter, disclosed herein. According to example 39, which encompassesexample 38, above, method 400 further comprises (block 470) selectingthe value of the flow characteristic of gas 101 at the predeterminedpoint in laser focal plane 108 as a reference test parameter foroperating additive-manufacturing machine 100.

When the difference between the value of the physical property atpredetermined location 192 on or underneath test-coupon peripheralsurface 191 and the desired value of the physical property is within thepredetermined range for first set of process parameters 161, first setof process parameters 161 can be selected for operatingadditive-manufacturing machine 100. First set of process parameters 161are controlled externally and, in some examples, are not able to accountfor some internal variations of additive-manufacturing machine 100(e.g., filter cleanness). At the same time, first set of processparameters 161 was previously used to flow gas 101 within chamber 102and to identify the value of the flow characteristic of gas 101 at thepredetermined point in laser focal plane 108. The value of the flowcharacteristic of gas 101 accounts for various internal variations ofadditive-manufacturing machine 100 (in addition to changes to first setof process parameters 161). As such, the value of the flowcharacteristic of gas 101 can be used for internal control and, moregenerally, as a reference test parameter for operatingadditive-manufacturing machine 100.

For example, flow-characterization system 150 can be periodicallyinstalled into additive-manufacturing machine 100, and gas 101 is flownwithin chamber 102 in accordance with first set of process parameters161. Flow-characterization system 150 determined the value of the flowcharacteristic of gas 101 at the predetermined point in laser focalplane 108 and this value can be compared to the reference test parameterto ensure that no changes to additive-manufacturing machine 100 haveoccurred and that additive-manufacturing machine 100 can continue tooperate.

Referring generally to FIGS. 1 and 5 and particularly to, e.g., FIGS.2B-2E for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 40 of the subjectmatter, disclosed herein. According to example 40, method 500 ofmonitoring operation of additive-manufacturing machine 100 thatcomprises chamber 102, platform 107, movable inside chamber 102 andcomprising build-plane surface 105, and laser 106, having laser focalplane 108 within chamber 102, is provided. Method 500 comprises a stepof (block 510) flowing gas 101 within chamber 102. in accordance withfirst set of process parameters 161. Method 300 also comprises a step of(block 520) identifying a value of a flow characteristic of gas 101 at apredetermined point in laser focal plane 108 while flowing gas 101within chamber 102 in accordance with first set of process parameters161. Method 300 further comprises a step of (block 540) comparing thevalue of flow characteristic of gas 101 at the predetermined point inlaser focal plane 108 to a desired value of flow characteristic todetermine a difference therebetween. Method 300 additionally comprises astep of (block 550) additively manufacturing part 198, using laser 106,while flowing gas 101 within chamber 102 in accordance with first set ofprocess parameters 161, only when the difference between the value offlow characteristic of gas 101 at the predetermined point in laser focalplane 108 and the desired value of flow characteristic is within apredetermined range.

The desired value of flow characteristics can be used as a directreference to determine if additive-manufacturing machine 100 is readyfor manufacturing part 198. This direct reference eliminates the needfor additively manufacturing test coupons and testing these couponsthereafter. Furthermore, this direct reference eliminates the need forsimulations and computational-fluid-dynamics analysis. For example, thedesired value of flow characteristic can be established previouslyduring validation and/or qualification of additive-manufacturing machine100.

Gas 101 is flown using various components of additive-manufacturingmachine 100 as, e.g., is shown in FIG. 2B. For example, fan 118 directsgas 101 to inlet 112 and additional inlet 113, through which gas 101enters chamber 102. Gas 101 passes through chamber 102 and exits throughoutlet 114. In some examples, gas 101 is passed through filter 116 toremove any contaminants before being returned back into chamber 102.This recirculation of gas 101 through chamber 102 removes contaminantsand helps to keep the laser path unobstructed. The effectiveness of thisgas recirculation process depends on the flow characteristic of gas 101.The flow characteristic is identified at one or more specific locationswithin chamber 102, such as predetermined point 109 in laser focal plane108 while flowing gas 101 within chamber 102. Furthermore, the flowcharacteristic of gas 101 or, more specifically, the value of the flowcharacteristic of gas 101 depends on the process parameters (e.g., firstset of process parameters 161) within chamber 102.

Referring generally to FIGS. 1 and 5 and particularly to, e.g., FIG. 2Bfor illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 41 of the subjectmatter, disclosed herein. According to example 41, which encompassesexample 40, above, method 500 further comprises, based on the value offlow characteristic of gas 101 at the predetermined point in laser focalplane 108, (block 560) simulating the step of flowing gas 101 withinchamber 102 in accordance with first set of process parameters 161 sothat a value of a simulated-flow characteristic of gas 101 isidentified. First set of process parameters 161 is selected to besuitable for operating additive-manufacturing machine 100 only when thedifference between the value of the simulated-flow characteristic of gas101 at the predetermined point away from laser focal plane 108 and adesired value of simulated-flow characteristic is within a predeterminedsimulated range.

Simulating the step of flowing gas 101 within chamber 102 based on thevalue of flow characteristic of gas 101 at the predetermined point inlaser focal plane 108 can be used instead of additively manufacturingtest coupon (e.g., to expedite the system qualification) or in additionto additively manufacturing the test coupon (e.g., to provide additionalfeedback). First set of process parameters 161 is used as an input tothis simulation. As such, any changes to these process parameters canresult in changes to the value of the simulated-flow characteristic ofgas 101 at the predetermined point away from laser focal plane 108. Thisfeedback is used to determine process parameters that yield the desiredvalue of the simulated-flow characteristic, e.g., the one within thepredetermined range.

Process parameters can be changed (e.g., from first set of processparameters 161 to second set of process parameters 162) until thedifference between the value of the simulated-flow characteristic andthe desired value of the physical property is within the predeterminedrange.

Referring generally to FIGS. 1 and 5 and particularly to, e.g., FIGS.2B, 2C, and 2E for illustrative purposes only and not by way oflimitation, the following portion of this paragraph delineates example42 of the subject matter, disclosed herein. According to example 42,which encompasses of example 40 or 41, above, first set of processparameters 161 comprises at least one of a fan speed, a filter type, oran orientation of a flow curtain within chamber 102.

The flow characteristic of gas 101 or, more specifically, the value ofthe flow characteristic of gas 101 depends on the process parameters(e.g., first set of process parameters 161, second set of processparameters 162) within chamber 102. At the same time, the flowcharacteristic of gas 101 has an impact on the physical properties oftest coupon 190 or, more specifically, the physical property atpredetermined location 192 on or underneath test-coupon peripheralsurface 191. As such, these process parameters have an impact on thephysical property at predetermined location 192 on or underneathtest-coupon peripheral surface 191. Controlling each of these processparameters helps to achieve the desired physical property, e.g., whenthe difference between the value of the physical property atpredetermined location 192 on or underneath test-coupon peripheralsurface 191 and the desired value of the physical property is within thepredetermined range.

For example, a higher fan speed increases the speed, at which gas 101 isflown within chamber 102, and can help with faster and more efficientremoval of contaminants from chamber 102. A higher fan speed can beused, e.g., when the contamination level within chamber 102 is otherwisehigh and interferes with the laser beam as the laser beam passes fromlaser 106 to laser focal plane 108. However, excessive fan speeds cancause turbulence, vortexes, and other undesirable phenomena, which canbe captured as the flow characteristic of gas 101. A filter type alsoimpacts the speed, at which gas 101 can be flown within chamber 102,e.g., how much restriction to the gas flow is presented by filter 116.However, a filter type also determines the amount and the type ofcontaminants, removed from gas 101 before gas 101 is reintroduced intochamber 102. ln some examples, one or more flow curtains are used withinchamber 102 to redirect gas 110 within chamber 102, in addition to theinitial direction, provided by the inlets.

Referring generally to FIGS. 1 and 5 and particularly to, e.g., FIGS.2B, 2C, and 2E for illustrative purposes only and not by way oflimitation, the following portion of this paragraph delineates example43 of the subject matter, disclosed herein. According to example 43,which encompasses any one of examples 40 to 42, above, the step of(block 520) identifying the value of flow characteristic of gas 101 atthe predetermined point in laser focal plane 108 comprises (block 522)determining static-pressure values at multiple points in laser focalplane 108 and (block 524) analyzing the static-pressure values todetermine the value of flow characteristic of gas 101 at predeterminedpoint 109 in laser focal plane 108.

The static-pressure values at multiple points in laser focal plane 108are representative of the various flow characteristics of gas 101, suchas the direction of gas 101 within chamber 102 and the speed, at whichgas 101 travels through chamber 102. For example, the static-pressuredifference between two points can be used for these purposes. Thelocations of these points determine which flow characteristics of gas101 can be identified.

FIG. 2E illustrates multiple points (identified as reference-plateopenings 158 in reference plate 154 of flow-characterization system150). In some examples, the difference or, more generally, thevariations of the static-pressure values among different points in laserfocal plane 108 can be used to determine the value of flowcharacteristic of gas 101 at predetermined point 109 in laser focalplane 108. For example, two points, located along the X-axis, can havedifferent static-pressure values. This difference can be correlated tothe gas flow along the X-axis. In some examples, predetermined point 109in laser focal plane 108 coincides with one of the multiple points inlaser focal plane 108, at which the static-pressure values areidentified. Alternatively, predetermined point 109 in laser focal plane108 is positioned between two or more of the multiple points in laserfocal plane 108.

Referring generally to FIGS. 1 and 5 and particularly to, e.g., FIG. 2Bfor illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 44 of the subjectmatter, disclosed herein. According to example 44, which encompassesexample 43, above, the static-pressure values at the multiple points inlaser focal plane 108 within chamber 102 are determined usingcomputational-fluid-dynamics analysis.

Computational-fluid-dynamics analysis enables the static-pressure valuesat the multiple points in laser focal plane 108 within chamber 102 to bedetermined without performing an actual test and using any test probes,thereby saving time and eliminating the need for test equipment.

In some examples, computational-fluid-dynamics analysis enables thestatic-pressure values at any locations in laser focal plane 108 withinchamber 102 to be determined. Furthermore, in some examples,computational-fluid-dynamics analysis enables these locations to bechanged as needed, e.g., to provide a more specific correlation to thevalue of the physical property at predetermined location 192 on orunderneath test-coupon peripheral surface 191.

Referring generally to FIGS. 1 and 5 and particularly to, e.g., FIGS. 2Aand 2B for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 45 of the subjectmatter, disclosed herein. According to example 45, which encompasses anyone of examples 40 to 44, above, the flow characteristic of gas 101 is alinear flowrate of gas 101 at predetermined point 109 in laser focalplane 108.

The linear flowrate of gas 101 at predetermined point 109 in laser focalplane 108 is an indication of how fast contaminants are being removedfrom chamber 102. Furthermore, the linear flowrate of gas 101 can impactthermal conditions during sintering, e.g., a higher flowratecorresponding to more cooling. It should be noted that laser focal plane108 is where the sintering occurs during additive manufacturing.

In some examples, multiple linear flowrates of gas 101 are measuredwithin chamber 102, e.g., flowrates in different directions atpredetermined point 109 in laser focal plane 108 or flowrates atdifferent points, e.g., within laser focal plane 108 and/or away fromlaser focal plane 108.

Referring generally to FIGS. 1 and 5 and particularly to, e.g., FIG. 2Bfor illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 46 of the subjectmatter, disclosed herein. According to example 46, which encompasses anyone of examples 40 to 45, laser 106 is not operational during the stepof (block 520) identifying the value of flow characteristic of gas 101.

With laser 106 not being operational, various metrology tools can bepositioned within chamber 102 to determine the flow characteristic ofgas 101 and without any risk of being damaged by laser 106. For example,flow-characterization system 150 can be placed on platform 107 ofadditive-manufacturing machine 100 to determine the flow characteristicof gas 101. It should be noted that platform 107 is in the direct lineof sight of laser 106.

The operation of laser 106 does not impact the flow characteristic ofgas 101 within chamber 102. As such, the value of the flowcharacteristic of gas 101 at predetermined point 109 in laser focalplane 108 while flowing gas 101 within chamber 102 in accordance withfirst set of process parameters 161 will be the same when laser 106 isoperational and when laser 106 is not operational.

Referring generally to FIGS. 1 and 5 and particularly to, e.g., FIGS.2B-2E for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 47 of the subjectmatter, disclosed herein. According to example 47, which encompasses anyone of examples 40 to 46, the step of (block 520) identifying the valueof flow characteristic of gas 101 at the predetermined point in laserfocal plane 108 is performed using flow-characterization system 150,comprising pressure probes 152 and reference plate 154 that comprisesdatum surface 156 and reference-plate openings 158, passing throughdatum surface 156. Datum surface 156 is coplanar with laser focal plane108 during the step of (block 520) identifying the value of flowcharacteristic of gas 101. Each of pressure probes 152 is received by arespective one of reference-plate openings 158 and is configured tomonitor static pressure at datum surface 156 of reference plate 154.

Flow-characterization system 150 is specifically configured foridentifying the value of flow characteristic of gas 101 at thepredetermined point in laser focal plane 108. The predetermined point inlaser focal plane 108 is determined by the position of reference-plateopenings 158 or, more specifically, by pressure probes 152, positionedin reference-plate openings 158. Pressure probes 152 obtained variouscharacteristics, which are combined to identify the value of flowcharacteristic of gas 101 at the predetermined point in laser focalplane 108.

Flow-characterization system 150 is positioned on platform 107 whenlaser 106 is not operational. As such, flow-characterization system 150is not damaged by laser 106 while identifying the value of flowcharacteristic of gas 101 at the predetermined point in laser focalplane 108. Flow-characterization system 150 comprises pressure probes152 for determining, e.g., static pressure at multiple locations.Flow-characterization system 150 also comprises reference plate 154 thatcomprises datum surface 156 and reference-plate openings 158, passingthrough datum surface 156. Datum surface 156 is coplanar with laserfocal plane 108 while identifying the value of flow characteristic ofgas 101. This positioning ensures that the flow characteristic of gas101 is determined at the predetermined point in laser focal plane 108(and not away from laser focal plane 108). Each of pressure probes 152is received by a respective one of reference-plate openings 158. lnother words, reference-plate openings 158 determine the locations ofpressure probes 152. Referring to FIG. 2C, in some examples, pressureprobes 152 are positioned below datum surface 156 to ensure that thestatic pressure (at datum surface 156 of reference plate 154) isaccurately measured and not impacted by the flow of gas 101 above datumsurface 156.

Referring generally to FIGS. 1 and 5 and particularly to, e.g., FIG. 2Bfor illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 48 of the subjectmatter, disclosed herein. According to example 48, which encompassesexample 47, above, method 300 further comprises, prior to the step of(block 520) identifying the value of the flow characteristic of gas 101at predetermined point 109 in laser focal plane 108, (block 512)positioning flow-characterization system 150 onto build-plane surface105 of platform 107. Method 300 also comprises (block 514) positioningplatform 107 so that datum surface 156 of reference plate 154 offlow-characterization system 150 is coplanar with laser focal plane 108.

Platform 107 provides the alignment of datum surface 156, relative tolaser focal plane 108 or, more specifically, ensures that datum surface156 is coplanar with laser focal plane 108. This alignment ensures thatthe flow characteristic of gas 101 is determined at the predeterminedpoint in laser focal plane 108 (and not away from laser focal plane108).

For example, flow-characterization system 150 has a height (extending inthe Z-direction). This height ensures that various external componentsof flow-characterization system 150 can be arranged and, if needed,accessed (e.g., while servicing flow-characterization system 150).Before positioning flow-characterization system 150, platform 107 can bepositioned such that a powder layer is at laser focal plane 108.However, this powder layer can be much thinner /shorter thanflow-characterization system 150. As such, if flow-characterizationsystem 150 is positioned on platform 107 without adjusting the height ofplatform 107, then datum surface 156 will be above laser focal plane108. Taking measurements at this location (above laser focal plane 108)are not useful, at least for some application. Platform 107 is thereforelowered until datum surface 156 is coplanar with laser focal plane 108.

Referring generally to FIGS. 1 and 5 and particularly to, e.g., FIG. 2Bfor illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 49 of the subjectmatter, disclosed herein. According to example 49, which encompassesexample 47 or 48, above, method 300 further comprises, after the step of(block 520) identifying the value of the flow characteristic of gas 101at the predetermined point in laser focal plane 108 and prior to thestep of (block 550) additively manufacturing part 198, (block 528)removing flow-characterization system 150 from platform 107 and (block529) positioning platform 107 so that build-plane surface 105 ofplatform 107 is coplanar with laser focal plane 108.

Once the value of the flow characteristic of gas 101 is identified,flow-characterization system 150 is removed from platform 107. It shouldbe noted that during the operation of flow-characterization system 150,build-plane surface 105 of platform 107 is below laser focal plane 108,while datum surface 156 of reference plate 154 of flow-characterizationsystem 150 is coplanar with laser focal plane 108. Once the value of theflow characteristic of gas 101 is identified, additive-manufacturingmachine 100 needs to be returned to an operational state, in whichbuild-plane surface 105 of platform 107 is coplanar with laser focalplane 108. As such, platform 107 is raised until build-plane surface 105is coplanar with laser focal plane 108. In this state, build-planesurface 105 of platform 107 is ready to receive a precursor (e.g.,powder) for additive manufacturing.

In some examples, platform 107 is equipped with one or more linearactuators used for lowering and raising platform 107. Some examplesinclude, but are not limited to threaded rods, pneumatic cylinders,scotch yokes, and solenoids.

Referring generally to FIGS. 1 and 5 and particularly to, e.g., FIGS.2B-2D for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 50 of the subjectmatter, disclosed herein. According to example 50, which encompasses anyone of examples 47 to 49, flow-characterization system 150 furthercomprises extensible pressure probe 153, protruding above datum surface156 of reference plate 154. Method 300 further comprises a step of(block 525) identifying a value of an additional flow characteristic ofgas 101 at an additional predetermined point, spaced away from laserfocal plane 108, using extensible pressure probe 153.

The value of the additional flow characteristic of gas 101 at theadditional predetermined point, spaced away from laser focal plane 108,provides an additional characterization of the gas flow within chamber102. This value can be used together with the value of the physicalproperty at predetermined location 192 on or underneath test-couponperipheral surface 191 to provide a more comprehensive view of the gasflow within chamber 102.

For example, the value of the additional flow characteristic of gas 101at the additional predetermined point can be compared with the value ofthe flow characteristic of gas 101 at predetermined point 109, e.g., todetermine any variations of the flow characteristic along the Z-axis ofchamber 102. It should be noted that the laser beam travels from laser106 to focal plane 108 along the Z-axis of chamber 102. As such, thevalue of the additional flow characteristic of gas 101 at the additionalpredetermined point provides additional input.

Extensible pressure probe 153 can be supported using reference plate 154as, e.g., is shown in FIGS. 2C and 2D. In some examples, inlet probe 157is used to identify the value of the additional flow characteristic ofgas 101 at the additional predetermined point, spaced away from laserfocal plane 108. This additional predetermined point can be positionedat one of the chamber inlets as, e.g., is schematically shown in FIG.2B.

Referring generally to FIGS. 1 and 5 and particularly to, e.g., FIGS.2B-2D for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 51 of the subjectmatter, disclosed herein. According to example 51, which encompassesexample 50, above, the step of (block 525) identifying the value of theadditional flow characteristic of gas 101 at the additionalpredetermined point, spaced away from laser focal plane 108, usingextensible pressure probe 153, and the step of (block 520) identifyingthe value of the flow characteristic of gas 101 at predetermined point109 in laser focal plane 108 overlap in time.

A combination of the additional flow characteristic of gas 101 at theadditional predetermined point and the flow characteristic of gas 101 atpredetermined point 109 provide a more comprehensive analysis of theflow conditions within chamber 102 than either one of these flowcharacteristics on its own. The cumulative effect is achieved when thecorresponding values of these flow characteristics are obtained withinthe same timeframe. In other words, both values characterize the samegas flow condition within the chamber.

For example, identifying the value of the additional flow characteristicof gas 101 at the additional predetermined point and identifying thevalue of the flow characteristic of gas 101 at predetermined point 109can start and end at the same time. In other examples, the start timeand/or end time can be different. In other words, these twoidentification operations are staggered in time.

Referring generally to FIGS. 1 and 5 and particularly to, e.g., FIGS.2B-2D for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 52 of the subjectmatter, disclosed herein. According to example 52, which encompassesexample 50, above, flow-characterization system 150 further comprisesactuator 159, coupled to extensible pressure probe 153. The step of(block 525) Identifying the value of the additional flow characteristicof gas 101 at the additional predetermined point, spaced away from laserfocal plane 108, using extensible pressure probe 153, comprises (block526) moving extensible pressure probe 153 relative to datum surface 156of reference plate 154 in a direction, perpendicular to datum surface156 using actuator 159.

Actuator 159 enables the position of extensible pressure probe 153 to bechanged relative to datum surface 156, e.g., as schematically shown inFIGS. 2C and 2D. As such, actuator 159 controls the position of theadditional predetermined point relative to datum surface 156. Thisposition can be changed, using actuator 159, to obtain even more values,each corresponding to a different position of the additionalpredetermined point relative to datum surface 156 of reference plate154.

Various examples of actuator 159 are contemplated, such as motorizedthreaded rods, pneumatic cylinders, scotch yokes, and solenoids.Actuator 159 can be positioned within an enclosure offlow-characterization system 150 to prevent interference with the gasflow within chamber 102. For example, actuator 159 can be positionedbelow datum surface 156, relative to laser 106.

Referring generally to FIGS. 1 and 5 and particularly to, e.g., FIGS. 2Cand 2D for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 53 of the subjectmatter, disclosed herein. According to example 53, which encompassesexample 52, above, method 300 further comprises a step of (block 527)identifying, at additional predetermined points, the values ofadditional flow characteristics of gas 101. At least one of theadditional predetermined points is farther away from laser focal plane108 than at least another one of the additional predetermined points.

Measuring the flow characteristics of gas 101 at additional pointsprovides additional input, resulting in a more comprehensive analysis ofthe flow conditions within chamber 102. The laser beam travels fromlaser 106 to focal plane 108 along the Z-axis of chamber 102. As such,the gas flow at various distances away from laser focal plane 108 canimpact this laser-beam travel. For example, the contamination away fromlaser focal plane 108 can impact the passage of the laser beam to focalplane 108.

In some examples, these additional predetermined points are selectedbased on the height of chamber 102, vertical positions of the variousinlets and outlets into the chamber, the orientation of the inlets, andother factors.

Referring generally to FIGS. 1 and 5 and particularly to, e.g., FIGS. 2Cand 2D for illustrative purposes only and not by way of limitation, thefollowing portion of this paragraph delineates example 54 of the subjectmatter, disclosed herein. According to example 54, which encompassesexample 53, above, the step of (block 527) identifying, at theadditional predetermined points, the values of the additional flowcharacteristics of gas 101 is performed using extensible pressure probe153.

Extensible pressure probe 153 can change the measurement positionrelative to datum surface 156 of reference plate 154 and also relativeto laser focal plane 108. As such, extensible pressure probe 153 canobtain multiple measurements within chamber 102, which provide a morecomprehensive analysis of the flow conditions within chamber 102.

In some examples, these additional predetermined points are selectedbased on the height of chamber 102, vertical positions of the variousinlets and outlets into the chamber, the orientation of the inlets, andother factors.

Different examples of the apparatus(es) and method(s) disclosed hereininclude a variety of components, features, and functionalities. Itshould be understood that the various examples of the apparatus(es) andmethod(s), disclosed herein, may include any of the components,features, and functionalities of any of the other examples of theapparatus(es) and method(s) disclosed herein in any combination.

Many modifications of examples, set forth herein, will come to mind ofone skilled in the art, having the benefit of the teachings, presentedin the foregoing descriptions and the associated drawings.

Therefore, it is to be understood that the subject matter, disclosedherein, is not to be limited to the specific examples illustrated andthat modifications and other examples are intended to be included withinthe scope of the appended claims. Moreover, although the foregoingdescription and the associated drawings describe examples of the subjectmatter, disclosed herein, in the context of certain illustrativecombinations of elements and/or functions, it should be appreciated thatdifferent combinations of elements and/or functions may be provided byalternative implementations without departing from the scope of theappended claims. Accordingly, parenthetical reference numerals in theappended claims are presented for illustrative purposes only and are notintended to limit the scope of the claimed subject matter to thespecific examples provided herein.

1. A method of configuring an additive-manufacturing machine thatcomprises a chamber, a platform, movable inside the chamber andcomprising a build-plane surface, and a laser, having a laser focalplane within the chamber, the method comprising steps of: ;flowing a gaswithin the chamber in accordance with a first set of process parametersidentifying a value of a flow characteristic of the gas at apredetermined point in the laser focal plane while flowing the gaswithin the chamber in accordance with the first set of processparameters; additively manufacturing a test coupon using the laser whileflowing the gas within the chamber in accordance with the first set ofprocess parameters, wherein the test coupon has a test-coupon peripheralsurface; comparing a value of a physical property at a predeterminedlocation on or underneath the test-coupon peripheral surface to adesired value of the physical property; and flowing the gas within thechamber in accordance with a second set of process parameters, differentfrom the first set of process parameters, when a difference between thevalue of the physical property at the predetermined location on orunderneath the test-coupon peripheral surface and the desired value ofthe physical property is outside of a predetermined range.
 2. The methodaccording to claim 1, wherein each of the first set of processparameters and the second set of process parameters comprises at leastone of a fan speed, a filter type, or an orientation of a flow curtainwithin the chamber.
 3. The method according to claim 1, wherein the stepof identifying the value of the flow characteristic of the gas at thepredetermined point in the laser focal plane comprises: determiningstatic-pressure values at multiple points in the laser focal plane, andanalyzing the static-pressure values to determine the value of the flowcharacteristic of the gas (101) at the predetermined point in the laserfocal plane.
 4. The method according to claim 3, wherein thestatic-pressure values at the multiple points in the laser focal planewithin the chamber are determined using computational-fluid-dynamicsanalysis.
 5. The method according to claim 1, wherein the flowcharacteristic of the gas is a linear flowrate of the gas at thepredetermined point in the laser focal plane.
 6. The method according toclaim 1, wherein the laser is not operational during the step ofidentifying the value of the flow characteristic of the gas.
 7. Themethod according to claim 1, wherein: the step of identifying the valueof the flow characteristic of the gas at the predetermined point in thelaser focal plane is performed using a flow-characterization system,comprising pressure probes and a reference plate that comprises a datumsurface and reference-plate openings, passing through the datum surface;the datum surface is coplanar with the laser focal plane during the stepof identifying the value of the flow characteristic of the gas; and eachof the pressure probes is received by a respective one of thereference-plate openings and is configured to monitor static pressure atthe datum surface of the reference plate.
 8. The method according toclaim 7, further comprising: prior to the step of identifying the valueof the flow characteristic of the gas at the predetermined point in thelaser focal plane, positioning the flow-characterization system onto thebuild-plane surface of the platform; and positioning the platform sothat the datum surface of the reference plate of theflow-characterization system is coplanar with the laser focal plane. 9.The method according to claim 7, further comprising, after the step ofidentifying the value of the flow characteristic of the gas at thepredetermined point in the laser focal plane and prior to the step ofadditively manufacturing the test coupon: removing theflow-characterization system from the platform; and positioning theplatform so that the build-plane surface of the platform is coplanarwith the laser focal plane.
 10. The method according to claim 7,wherein: the flow-characterization system further comprises anextensible pressure probe, protruding above the datum surface of thereference plate; and the method further comprises a step of identifyinga value of an additional flow characteristic of the gas at an additionalpredetermined point, spaced away from the laser focal plane, using theextensible pressure probe.
 11. The method according to claim 10, whereinthe step of identifying the value of the additional flow characteristicof the gas at the additional predetermined point, spaced away from thelaser focal plane, using the extensible pressure probe and the step ofidentifying the value of the flow characteristic of the gas at thepredetermined point in the laser focal plane overlap in time.
 12. Themethod according to claim 11, wherein: the flow-characterization systemfurther comprises an actuator, coupled to the extensible pressure probe;and the step of identifying the value of the additional flowcharacteristic of the gas at the additional predetermined point, spacedaway from the laser focal plane, using the extensible pressure probe,comprises moving the extensible pressure probe relative to the datumsurface of the reference plate in a direction perpendicular to the datumsurface using the actuator.
 13. The method according to claim 11,further comprising a step of identifying, at additional predeterminedpoints, values of additional flow characteristics of the gas, wherein atleast one of the additional predetermined points is farther away fromthe laser focal plane than at least another one of the additionalpredetermined points.
 14. The method according to claim 13, wherein thestep of identifying, at the additional predetermined points, theadditional flow characteristics of the gas is performed using theextensible pressure probe.
 15. The method according to claim 1, whereinthe second set of process parameters is determined based on the value ofthe physical property at the predetermined location on or underneath thetest-coupon peripheral surface and further based on the first set ofprocess parameters.
 16. The method according to claim 1, wherein thesecond set of process parameters is determined based on the value of theflow characteristic of the gas at the predetermined point in the laserfocal plane and further based on the value of the physical property atthe predetermined location on or underneath the test-coupon peripheralsurface.
 17. The method of claim 1, further comprising steps of:identifying a value of the flow characteristic of the gas at thepredetermined point in the laser focal plane while flowing the gaswithin the chamber in accordance with the second set of processparameters; additively manufacturing a second test coupon using thelaser while flowing the gas within the chamber in accordance with thesecond set of process parameters, wherein the second test coupon has asecond-test-coupon peripheral surface; comparing a value of the physicalproperty at a second predetermined location on or underneath thesecond-test-coupon peripheral surface to the desired value of thephysical property; and flowing the gas within the chamber in accordancewith a third set of process parameters , different from the first set ofprocess parameters and from the second set of process parameters, when adifference between the value of the physical property at the secondpredetermined location on or underneath the second-test-couponperipheral surface and the desired value of the physical property isoutside of the predetermined range.
 18. The method according to claim 1,further comprising selecting the first set of process parameters foroperating the additive-manufacturing machine when the difference betweenthe value of the physical property at the predetermined location on orunderneath the test-coupon peripheral surface and the desired value ofthe physical property is within the predetermined range. 19-54.(canceled)
 55. The method according to claim 18, further comprisingselecting the value of the flow characteristic of the gas at thepredetermined point in the laser focal plane as a reference testparameter for operating the additive-manufacturing machine.
 56. Themethod according to claim 1, wherein the step of additivelymanufacturing the test coupon comprises: placing a powder layer onto thebuild-plane surface of the platform; and heating the powder layer withthe laser to locally melt the powder layer.